Engineering nonphotosynthetic carbon fixation for production of bioplastics by methanogenic archaea

Kershanthen Thevasundaram, Joseph J. Gallagher, Freeman Cherng, Michelle C.Y. Chang

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The conversion of CO2 to value-added products allows both capture and recycling of greenhouse gas emissions. While plants and other photosynthetic organisms play a key role in closing the global carbon cycle, their dependence on light to drive carbon fixation can be limiting for industrial chemical synthesis. Methanogenic archaea provide an alternative platform as an autotrophic microbial species capable of non-photosynthetic CO2 fixation, providing a potential route to engineered microbial fermentation to synthesize chemicals from CO2 without the need for light irradiation. One major challenge in this goal is to connect upstream carbon-fixation pathways with downstream biosynthetic pathways, given the distinct differences in metabolism between archaea and typical heterotrophs. We engineered the model methanogen, Methanococcus maripaludis, to divert acetyl-coenzyme A toward biosynthesis of value-added chemicals, including the bioplastic polyhydroxybutyrate (PHB). A number of studies implicated limitations in the redox pool, with NAD(P)(H) pools in M. maripaludis measured to be <15% of that of Escherichia coli, likely since methanogenic archaea utilize F420 and ferredoxins instead. Multiple engineering strategies were used to precisely target and increase the cofactor pool, including heterologous expression of a synthetic nicotinamide salvage pathway as well as an NAD+-dependent formate dehydrogenase from Candida boidinii. Engineered strains of M. maripaludis with improved NADH pools produced up to 171 ± 4 mg/L PHB and 24.0 ± 1.9% of dry cell weight. The metabolic engineering strategies presented in this study broaden the utility of M. maripaludis for sustainable chemical synthesis using CO2 and may be transferable to related archaeal species.

Original languageEnglish (US)
Article numbere2118638119
JournalProceedings of the National Academy of Sciences of the United States of America
Volume119
Issue number23
DOIs
StatePublished - Jun 7 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • archaea
  • bioplastics
  • carbon fixation
  • metabolic engineering
  • redox cofactors

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